Present day data networks typically comprise routers or other types of switches that route customer data packets over one or more links (e.g., virtual circuits) between a data source (e.g., a customer's computer connected to the data network) and destination. Successful routing of customer data packets requires that a logical path (a collection of one or more links) exist in the network between the source and destination for that packet. Based on the contents of its routing table, each router along the path ascertains from the data packet it receives the identity of the downstream router (or data destination) to receive the packet. Assuming the network possesses sufficient physical redundancy (e.g., multiple routers, multiple links), the network can dynamically redefine paths using protocols such as the Border Gateway Protocol (BGP) or Open Shortest Path First (OSPF) protocol, in case of a router or link failure. The use of such protocols ensures that no one router or link failure disrupts the flow of packets between a data source and destination.
Numerous commercial monitoring systems presently exist for detecting the operating status of routers. However, such systems typically provide local monitoring of the routers themselves, focusing on whether the routers successfully responded to a connectivity test request. Because current data networks enjoy redundancy (i.e., multiple physical paths may potentially exist between any data source and destination), one or more router failures do not necessarily indicate a customer connectivity trouble. Such present day monitoring systems ignore a key requirement for customer connectivity, namely that a path must exist between a prescribed data source and data destination, as indicated by contents of each routing table. Typically, such prior art monitoring systems often falsely notified the network manager (i.e., the individual(s) responsible for network oversight) of a customer connectivity trouble, requiring the network manager probe the network further. Often, the network manager had to spend large amounts of time to determine the cause of the customer connectivity trouble. In the past, most network managers used a non-deterministic monitoring methodology to determine customer connectivity failures. Often, a customer would detect the trouble first before the network manager, usually leading to customer dissatisfaction.
Thus, there is need for a technique for detecting and isolating customer connectivity troubles.